This article discusses the major parameters that affect fluorescent lamp performance under fixture conditions. These parameters include fixture type, and HVAC integration, which directly determine the minimum lamp wall temperature (MLWT), and therefore, the resulting light output of the lamp/ballast system. Experimental data is presented showing that the lumen output of the lamp/ballast system can vary by as much as 20% and that the system efficacy can vary by 10% depending upon the type of fixture and HVAC system employed.